1. Field of the Invention
The present invention generally relates to probes for use in the testing of electronic components and, more particularly, to the structure and process for the fabrication of probes particularly adapted for automated testing of electronic equipment and components.
2. Description of the Prior Art
The testing of electrical equipment and components typically requires the establishment of temporary circuits by which electrical voltages and currents in the circuit or component can be sensed or inferred from voltages appearing at particular points of the circuit or component. In the manufacture of components or complete circuits of substantial complexity, such test steps have become a normal part of the manufacturing process. In circumstances where large numbers of such circuits or components are manufactured, it is common to automate the testing process which is carried out at one or more points during the manufacturing process.
The formation of the temporary circuit is typically done by means of one or more probes which allow electrical contact with the circuit or component to be made in a small, well-defined area. The use of a probe can often avoid the possibility of engendering spurious connection of different parts of the circuit or component which could damage the same when operational levels of voltage and current are applied thereto, as is often necessary for effective functional testing to take place. This function of a probe is often enhanced by the provision of a relatively sharply pointed contact tip; the sharpness of the point being such as to inherently avoid bridging of conductors of the electrical circuit or component. The sharpness of the point can also be useful in penetrating or dislodging contamination and oxidation to increase the reliability of the electrical contact.
Automation of the testing process usually involves the bringing of a plurality of probes into contact with the electrical circuit or component by mechanical means. This often poses difficulties, particularly when plural probes are simultaneously applied to the circuit or component. Dimensional variations from unit to unit and within each unit under test (UUT) may cause problems by some probes failing to contact the UUT concurrently with contact by other probes. Increasing proximity of the UUT and the mechanism carrying the probes can cause breakage of some of the probes. Broken probes can cause ambiguity of testing, especially when so-called go/no-go tests are performed, and expensive down-time of the automated test apparatus while the probe is replaced.
In the formation of electrical connections without the bonding of conductors, it is common to provide resiliency of at least a portion of one or more of the contacting parts. U.S. Pat. Nos. 4,969,842 to Davis and 4,921,430 to Matsuoka are exemplary of such arrangements. Matsuoka provides a cantilever structure to provide resiliency of the conductors within a socket for an integrated circuit. Matsuoka also provides insulation on the resilient conductors to electrically separate the same in an IC socket. Multiple contact test probes having insulation between probe conductors are shown, for example, by U.S. Pat. No. 3,992,073 to Buchoff et al. The inclusion of other structures in the probe tip to improve response of the probe, for example to high frequencies, is taught by U.S. Pat. No. 4,116,523 to Coberly et al. The plating of materials to form conductors on an insulator for a coaxial connector is taught, for example, in U.S. Pat. No. 3,363,221 to Stark. The plating of conductors to improve electrical contact properties and the provision of additional metal to facilitate welding in the formation of an electrical connector is taught in U.S. Pat. No. 4,290,665 to Krasnov et al.
The increasing miniaturization of electronic circuits and components has also increased the precision required for the probes in automated testing machinery. To obtain sufficient accuracy in the dimensions of probes, it has been common to shape the probes or parts thereof by machining which is a costly and time-consuming process, resulting in a high cost for probes of presently used designs. The decreased size also has tended to increase breakage of the probes under conditions such as those described above. It is also possible that stresses placed on the small parts during the machining process tends to cause fatigue of the materials, also contributing to breakage and expenses of operating automated testing machinery.